Video imaging systems have been proposed for use in vehicles to monitor the driver and/or passengers in the vehicle. Some proposed imaging systems include one or two cameras focused on the driver of the vehicle to capture images of the driver's face and allow for determination of various facial characteristics of the driver including the position, orientation, and movement of the driver's eyes, face, and head. By knowing the driver facial characteristics, such as the driver's eye position and gaze, ocular data, head position, and other characteristics, vehicle control systems can provide enhanced vehicle functions. For example, a vehicle control system can monitor the eye of the driver and determine a condition in which the driver appears to be drowsy, and can take further action to alert the driver of the driver drowsy condition.
Many vehicle accidents are caused by the driver of the vehicle becoming drowsy and then falling asleep. In many driving situations, drivers are not even aware of their sleepiness or drowsiness prior to actually falling asleep. It has been proposed to monitor the facial characteristics of the vehicle driver, to anticipate when the driver is becoming drowsy, and to alert the driver before the driver falls asleep. One proposed technique employs video cameras focused on the driver's face for monitoring the eye of the driver. A vehicle mounted camera arrangement is disclosed in U.S. patent application Ser. No. 10/103,202, entitled “VEHICLE INSTRUMENT CLUSTER HAVING INTEGRATED IMAGING SYSTEM,” filed on Mar. 21, 2002, and commonly assigned to the Assignee of the present application The aforementioned vehicle camera arrangement includes a pair of video imaging cameras mounted in the instrument panel of the vehicle and focused on the facial characteristics, including the eyes, of the driver of the vehicle.
Prior known driver drowsiness detection techniques have proposed processing the video images from the cameras to determine a precise measurement of the percent of closure of both eyes of the driver. The percent of eye closure is then used to determine if the driver has become drowsy. For example, such approaches may monitor the eyelid position of each eye and determine a driver drowsiness condition based when the eyes of the driver are greater than or equal to eighty percent (80%) closure. While the aforementioned proposed technique is able to use the percent of closure of the eye of the driver as an indicator of driver drowsiness, such a technique is generally costly. Accordingly, it is therefore desirable to provide for an alternative low-cost driver drowsiness detection system for detecting a driver drowsy condition, particularly for use in a vehicle.